Recognition of microbial and mammalian phospholipid antigens by NKT cells with diverse TCRs

Abstract

CD1d-restricted natural killer T (NKT) cells include two major subgroups. The most widely studied are Vα14Jα18 + invariant NKT (iNKT) cells that recognize the prototypical α-galactosylceramide antigen, whereas the other major group uses diverse T-cell receptor (TCR) α-and β-chains, does not recognize α-galactosylceramide, and is referred to as diverse NKT (dNKT) cells. dNKT cells play important roles during infection and autoimmunity, but the antigens they recognize remain poorly understood. Here, we identified phosphatidylglycerol (PG), diphosphatidylglycerol (DPG, or cardiolipin), and phosphatidylinositol from Mycobacterium tuberculosis or Corynebacterium glutamicum as microbial antigens that stimulated various dNKT, but not iNKT, hybridomas. dNKT hybridomas showed distinct reactivities for diverse antigens. Stimulation of dNKT hybridomas by microbial PG was independent of Toll-like receptor-mediated signaling by antigen-presenting cells and required lipid uptake and/or processing. Furthermore, microbial PG bound to CD1d molecules and plate-bound PG/CD1d complexes stimulated dNKT hybridomas, indicating direct recognition by the dNKT cell TCR. Interestingly, despite structural differences in acyl chain composition between microbial and mammalian PG and DPG, lipids from both sources stimulated dNKT hybridomas, suggesting that presentation of microbial lipids and enhanced availability of stimulatory self-lipids may both contribute to dNKT cell activation during infection.

Polyclonal type II natural killer T cells require PLZF and SAP for their development and contribute to CpG-mediated antitumor response

“…Previous studies with type II NKT cell hybridomas have identified several self-lipid antigens recognized by type II NKT cells, including phospholipids, β-GlcCer, and sulfatide (27,(36)(37)(38)(39)(40). Interestingly, we found that 4get + type II NKT cells are potently activated by β-GlcCer containing C12:0 and C24:1 acyl chains, suggesting that a significant proportion of type II NKT cells recognize β-GlcCer.…”

Activation and Function of iNKT and MAIT Cells

“…However, iNKT cells cultured with infected macrophages stimulated their antimicrobial activity, which restricted bacterial growth. The results from an early study suggested that iNKT cells directly recognize certain purified phosphatidyl inositol mannosides from Mtb (Gilleron et al, 2001), and although this could not be confirmed using synthetic antigens ; subsequent work showed that Mtb-derived phosphatidylglycerol antigens were recognized by NKT cells with diverse TCR (Tatituri et al, 2013). Mice deficient for iNKT cells had a significantly higher number of granulomas, but the number of bacteria was similar to infected, control mice.…”

Type II NKT-TFH cells against Gaucher lipids regulate B-cell immunity and inflammation

“…A molar loading ratio (lipid to CD1d) of 200:1 was used for tetramerization studies for both mouse and human tetramers as used in other studies. 21,25 The unloaded multimer control was prepared by mixing CD1d tetramer with the carrier only.…”